Add (Sleep Mode) Similar to IOS Do Not Disturb function to an existing app.

Very simple request and straight forward code writing only. I have an app that is based on UILocalNotifications. These local notifications are fired every five minutes on hourly repeat intervals. So far, I have 24 notifications. All I want is to add a (Sleep Mode) function. Very similar to IOS Do not disturb. it should allow the user to select a sleep time and wake up time through two Date Pickers. I have set up these date pickers and got stuck on how to ignore or cancel these notifications through the period that user had specified and reschedule them again automatically while the app is in the background. If you have the ability, experience and knowledge to add such a function to an existing project, please let me know how long it would take you to do so and how much would it cost me?. Thank you.